That doesn't address the issue. If tax authorities require you to prove your tax basis, then you must unwind the anonymity. When you unwind it, you reduce the anonymity set for everyone that mixed with you.

It would be much better to be able to say, "okay here is my password" and the authorities still can't unwind it. I know how to design this. You then say you've kept all records and complied, but the system is too anonymous and this is not your fault. They would have to make it illegal to use the system. If we get to that stage, it will be Mad max war of the people against the government.